The sense of hearing in human beings involves the use of hair cells in the cochlea that convert or transduce audio signals into auditory nerve impulses. Hearing loss, which may be due to many different causes, is generally of two types: conductive and sensorineural. Conductive hearing loss occurs when the normal mechanical pathways for sound to reach the hair cells in the cochlea are impeded. These sound pathways may be impeded, for example, by damage to the auditory ossicles. Conductive hearing loss may often be helped by the use of conventional hearing aids that amplify sound so that audio signals reach the cochlea and the hair cells. Some types of conductive hearing loss may also be treated by surgical procedures.
Sensorineural hearing loss, on the other hand, is caused by the absence or destruction of the hair cells in the cochlea which are needed to transduce acoustic signals into auditory nerve impulses. People who suffer from sensorineural hearing loss may be unable to derive significant benefit from conventional hearing aid systems, no matter how loud the acoustic stimulus is. This is because the mechanism for transducing sound energy into auditory nerve impulses has been damaged. Thus, in the absence of properly functioning hair cells, auditory nerve impulses cannot be generated directly from sounds.
To overcome sensorineural hearing loss, numerous cochlear implant systems have been developed. Cochlear implant systems bypass the hair cells in the cochlea by presenting electrical stimulation directly to stimulation sites (e.g., auditory nerve fibers) by way of one or more channels formed by an array of electrodes implanted in a cochlear implant patient. Direct stimulation of the stimulation sites leads to the perception of sound in the brain and at least partial restoration of hearing function.
When a cochlear implant is initially implanted in a patient, and during follow up visits with a clinician (e.g., an audiologist) thereafter, it is usually necessary to fit the cochlear implant system to the patient. One of the goals of the fitting procedure is to optimize various program parameters (e.g., threshold levels (“T levels”), most comfortable stimulation levels (“M levels”), stimulation rates, input dynamic range (“IDR”) values, etc.) to fit the specific needs of the patient. Hence, a typical fitting session involves the psychophysical determination of various program parameters followed by further adjustments during live conversation with the patient in the clinic.
After a full fitting session, it is not uncommon for patients to complain of sub-optimal sound quality and hearing performance when they encounter conditions in the real-world (e.g., restaurants, classrooms, churches, etc.). It is currently impractical for clinics to test patients in these real-world acoustic scenarios. Consequently it is hard to make informed programming changes to ameliorate programming issues without significant amounts of trial and error.